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#mechanics

11 posts7 participants0 posts today
Public
Rxiv mechanobio

📰 "Retinotopic Mechanics derived using classical physics"
arxiv.org/abs/2109.11632 #Physics.Bio-Ph #Mechanics #Q-Bio.Nc #Dynamics #Cell

arXiv logo
arXiv.orgRetinotopic Mechanics derived using classical physicsThe concept of a cell$'$s receptive field is a bedrock in systems neuroscience, and the classical static description of the receptive field has had enormous success in explaining the fundamental mechanisms underlying visual processing. Borne out by the spatio-temporal dynamics of visual sensitivity to probe stimuli in primates, I build on top of this static account with the introduction of a new computational field of research, retinotopic mechanics. At its core, retinotopic mechanics assumes that during active sensing receptive fields are not static but can shift beyond their classical extent. Specifically, the canonical computations and the neural architecture that supports these computations are inherently mediated by a neurobiologically inspired force field (e.g.,$R_s\propto \sim 1 /ΔM$). For example, when the retina is displaced because of a saccadic eye movement from one point in space to another, cells across retinotopic brain areas are tasked with discounting the retinal disruptions such active surveillance inherently introduces. This neural phenomenon is known as spatial constancy. Using retinotopic mechanics, I propose that to achieve spatial constancy or any active visually mediated task, retinotopic cells, namely their receptive fields, are constrained by eccentricity dependent elastic fields. I propose that elastic fields are self-generated by the visual system and allow receptive fields the ability to predictively shift beyond their classical extent to future post-saccadic location such that neural sensitivity which would otherwise support intermediate eccentric locations likely to contain retinal disruptions is transiently blunted.
Public
Rxiv mechanobio

📰 "Retinotopic Mechanics derived using classical physics"
arxiv.org/abs/2109.11632 #Physics.Bio-Ph #Mechanics #Q-Bio.Nc #Dynamics #Cell

arXiv logo
arXiv.orgRetinotopic Mechanics derived using classical physicsThe concept of a cell$'$s receptive field is a bedrock in systems neuroscience, and the classical static description of the receptive field has had enormous success in explaining the fundamental mechanisms underlying visual processing. Borne out by the spatio-temporal dynamics of visual sensitivity to probe stimuli in primates, I build on top of this static account with the introduction of a new computational field of research, retinotopic mechanics. At its core, retinotopic mechanics assumes that during active sensing receptive fields are not static but can shift beyond their classical extent. Specifically, the canonical computations and the neural architecture that supports these computations are inherently mediated by a neurobiologically inspired force field (e.g.,$R_s\propto \sim 1 /ΔM$). For example, when the retina is displaced because of a saccadic eye movement from one point in space to another, cells across retinotopic brain areas are tasked with discounting the retinal disruptions such active surveillance inherently introduces. This neural phenomenon is known as spatial constancy. Using retinotopic mechanics, I propose that to achieve spatial constancy or any active visually mediated task, retinotopic cells, namely their receptive fields, are constrained by eccentricity dependent elastic fields. I propose that elastic fields are self-generated by the visual system and allow receptive fields the ability to predictively shift beyond their classical extent to future post-saccadic location such that neural sensitivity which would otherwise support intermediate eccentric locations likely to contain retinal disruptions is transiently blunted.
Public
Rxiv mechanobio

📰 "Extending the QMM Framework to the Strong and Weak Interactions"
arxiv.org/abs/2504.03817 #Physics.Gen-Ph #Mechanics #Matrix

arXiv logo
arXiv.orgExtending the QMM Framework to the Strong and Weak InteractionsWe extend the Quantum Memory Matrix (QMM) framework, originally developed to reconcile quantum mechanics and general relativity by treating space-time as a dynamic information reservoir, to incorporate the full suite of Standard Model gauge interactions. In this discretized, Planck-scale formulation, each space-time cell possesses a finite-dimensional Hilbert space that acts as a local memory, or quantum imprint, for matter and gauge field configurations. We focus on embedding non-Abelian SU(3)c (quantum chromodynamics) and SU(2)L x U(1)Y (electroweak interactions) into QMM by constructing gauge-invariant imprint operators for quarks, gluons, electroweak bosons, and the Higgs mechanism. This unified approach naturally enforces unitarity by allowing black hole horizons, or any high-curvature region, to store and later retrieve quantum information about color and electroweak charges, thereby preserving subtle non-thermal correlations in evaporation processes. Moreover, the discretized nature of QMM imposes a Planck-scale cutoff, potentially taming UV divergences and modifying running couplings at trans-Planckian energies. We outline major challenges, such as the precise formulation of non-Abelian imprint operators and the integration of QMM with loop quantum gravity, as well as possible observational strategies - ranging from rare decay channels to primordial black hole evaporation spectra - that could provide indirect probes of this discrete, memory-based view of quantum gravity and the Standard Model.
Public
Rxiv mechanobio

📰 "Retinotopic Mechanics derived using classical physics"
arxiv.org/abs/2109.11632 #Physics.Bio-Ph #Mechanics #Dynamics #Q-Bio.Nc #Cell

arXiv logo
arXiv.orgRetinotopic Mechanics derived using classical physicsThe concept of a cell$'$s receptive field is a bedrock in systems neuroscience, and the classical static description of the receptive field has had enormous success in explaining the fundamental mechanisms underlying visual processing. Borne out by the spatio-temporal dynamics of visual sensitivity to probe stimuli in primates, I build on top of this static account with the introduction of a new computational field of research, retinotopic mechanics. At its core, retinotopic mechanics assumes that during active sensing receptive fields are not static but can shift beyond their classical extent. Specifically, the canonical computations and the neural architecture that supports these computations are inherently mediated by a neurobiologically inspired force field (e.g.,$R_s\propto \sim 1 /ΔM$). For example, when the retina is displaced because of a saccadic eye movement from one point in space to another, cells across retinotopic brain areas are tasked with discounting the retinal disruptions such active surveillance inherently introduces. This neural phenomenon is known as spatial constancy. Using retinotopic mechanics, I propose that to achieve spatial constancy or any active visually mediated task, retinotopic cells, namely their receptive fields, are constrained by eccentricity dependent elastic fields. I propose that elastic fields are self-generated by the visual system and allow receptive fields the ability to predictively shift beyond their classical extent to future post-saccadic location such that neural sensitivity which would otherwise support intermediate eccentric locations likely to contain retinal disruptions is transiently blunted.
Public
Rxiv mechanobio

📰 "Tissue spreading couples gastrulation through extracellular matrix remodelling in early avian embryos"
biorxiv.org/content/10.1101/20 #Extracellular #Mechanics #Cell

bioRxiv · Tissue spreading couples gastrulation through extracellular matrix remodelling in early avian embryosTissue spreading (epiboly) couples gastrulation to shape the initial body plan of early vertebrate embryos. How these two large-scale collective cell movements cooperate remains unclear. Here, we examine the cell mechanics and tissue dynamics underlying epiboly of the chicken blastoderm. We found that cells at the blastoderm edge undergo a wetting-like process to spread on the vitelline membrane through stiffness sensing and cytoskeleton remodelling. This interaction is robust to edge cell loss and cooperates with cell-proliferation-based blastoderm growth to drive epiboly. Surprisingly, cellular movements during epiboly in turn remodel the extracellular matrix (ECM) to establish a basal lamina and maintain cell-cell connections. Impairing either edge cell wetting or the ECM causes tissue thickening and buckling in the across the blastoderm, disrupting gastrulation movements. We conclude that epiboly facilitates gastrulation by organizing an ECM that maintains a thin blastoderm. These findings suggest a general logic of mechanical coupling between distinctly controlled tissue movements during early development. ### Competing Interest Statement The authors have declared no competing interest.
Public
Rxiv mechanobio

📰 "The Quantum Memory Matrix: A Unified Framework for the Black Hole Information Paradox"
arxiv.org/abs/2504.00039 #Physics.Gen-Ph #Mechanics #Matrix

arXiv logo
arXiv.orgThe Quantum Memory Matrix: A Unified Framework for the Black Hole Information ParadoxWe present the Quantum Memory Matrix (QMM) hypothesis, which addresses the longstanding Black Hole Information Paradox rooted in the apparent conflict between Quantum Mechanics (QM) and General Relativity (GR). This paradox raises the question of how information is preserved during black hole formation and evaporation, given that Hawking radiation appears to result in information loss, challenging unitarity in quantum mechanics. The QMM hypothesis proposes that space-time itself acts as a dynamic quantum information reservoir, with quantum imprints encoding information about quantum states and interactions directly into the fabric of space-time at the Planck scale. By defining a quantized model of space-time and mechanisms for information encoding and retrieval, QMM aims to conserve information in a manner consistent with unitarity during black hole processes. We develop a mathematical framework that includes space-time quantization, definitions of quantum imprints, and interactions that modify quantum state evolution within this structure. Explicit expressions for the interaction Hamiltonians are provided, demonstrating unitarity preservation in the combined system of quantum fields and the QMM. This hypothesis is compared with existing theories, including the holographic principle, black hole complementarity, and loop quantum gravity, noting its distinctions and examining its limitations. Finally, we discuss observable implications of QMM, suggesting pathways for experimental evaluation, such as potential deviations from thermality in Hawking radiation and their effects on gravitational wave signals. The QMM hypothesis aims to provide a pathway towards resolving the Black Hole Information Paradox while contributing to broader discussions in quantum gravity and cosmology.
Public
Rxiv mechanobio

📰 "Fully GPU-Accelerated Immersed Boundary Method for Fluid-Structure Interaction in Complex Cardiac Models"
arxiv.org/abs/2503.22695 #Physics.Comp-Ph #Mechanics #Matrix

arXiv logo
arXiv.orgFully GPU-Accelerated Immersed Boundary Method for Fluid-Structure Interaction in Complex Cardiac ModelsFluid-structure interaction (FSI) plays a crucial role in cardiac mechanics, where the strong coupling between fluid flow and deformable structures presents significant computational challenges. The immersed boundary (IB) method efficiently handles large deformations and contact without requiring mesh regeneration. However, solving complex FSI problems demands high computational efficiency, making GPU acceleration essential to leverage massive parallelism, high throughput, and memory bandwidth. We present a fully GPU-accelerated algorithm for the IB method to solve FSI problems in complex cardiac models. The Navier-Stokes equations are discretized using the finite difference method, while the finite element method is employed for structural mechanics. Traditionally, IB methods are not GPU-friendly due to irregular memory access and limited parallelism. The novelty of this work lies in eliminating sparse matrix storage and operations entirely, significantly improving memory access efficiency and fully utilizing GPU computational capability. Additionally, the structural materials can be modeled using general hyperelastic constitutive laws, including fiber-reinforced anisotropic biological tissues such as the Holzapfel-Ogden (HO) model. Furthermore, a combined geometric multigrid solver is used to accelerate the convergence. The full FSI system, consisting of millions of degrees of freedom, achieves a per-timestep computation time of just 0.1 seconds. We conduct FSI simulations of the left ventricle, mitral valve, and aortic valve, achieving results with high consistency. Compared to single-core CPU computations, our fully GPU-accelerated approach delivers speedups exceeding 100 times.
Public
Philo Sophies

#Zoomposium with Prof. Dr. #Arieh #Ben-#Naim: “Demystifying #Entropy”

Information about the person and his scientific work

In another installment of our “Zoomposium series” on the topic of #physics and its #limits, my colleague Axel Stöcker from the “Blog der großen Fragen” and I had the opportunity to interview the renowned Israeli physical chemist Prof. Dr. Arieh Ben-Naim on the exciting topic of “Demystifying Entropy”.

Arieh, who was born on July 11, 1934, held a chair in #Physical #Chemistry at the Hebrew University of Jerusalem for over 40 years, with his main field of research being the theory of the #structure of #water, aqueous solutions and hydrophobic-hydrophilic interactions. He was mainly concerned with theoretical and experimental aspects of the general theory of #liquids and #solutions. In recent years, he has advocated the use of #information theory to better understand and advance #statistical #mechanics and #thermodynamics.

In this context, he has also worked intensively on the question of the nature and underlying principle of the phenomenon of #entropy, which he has published in numerous often cited but also controversially discussed popular science books.

The basic tenor of all his publications and lectures is that we need a new basic understanding of the phenomenon of entropy. In Arieh's view, entropy, which originally stems from the laws of #thermodynamics and in particular the 2nd law, has been misused and incorrectly transferred as a #concept to other areas of #physics, #biology and everyday #life.

In this respect, it was finally time (bon mot) to ask the author himself about his ground-breaking theses, which cast a different light on the #phenomenon of entropy or perhaps better said, bring entropy back to its place of origin.

The interview we conducted with him is in English.

Find out more at: philosophies.de/index.php/2024

or: youtu.be/Km88EreH4A8

photo of Arieh Ben-Naim
Public
Rxiv mechanobio

📰 "Soft matter mechanics of immune cell aggregates"
arxiv.org/abs/2503.21402 #Physics.Bio-Ph #Mechanical #Mechanics #Cell

arXiv logo
arXiv.orgSoft matter mechanics of immune cell aggregatesT-cells are a crucial subset of white blood cells that play a central role in the immune system. When T-cells bind antigens, it leads to cell activation and the induction of an immune response. If T-cells are activated by antigens in vivo or artificially in vitro, they form multicellular aggregates. The mechanical properties of such clusters provide valuable information on different T-cell activation pathways. Furthermore, the aggregate mechanics capture how T-cells are affected by mechanical forces and interact within larger conglomerates, such as lymph nodes and tumours. However, an understanding of collective T-cell adhesion and mechanics following cell activation is currently lacking. Probing the mechanics of fragile and microscopically small living samples is experimentally challenging. Here, the micropipette force sensor technique was used to stretch T-cell aggregates and directly measure their Young's modulus and ultimate tensile strength. A mechanistic model was developed to correlate how the stiffness of the mesoscale multicellular aggregate emerges from the mechanical response of the individual microscopic cells within the cluster. We show how the aggregate elasticity is affected by different activators and relate this to different activation pathways in the cells. Our soft matter mechanics study of multicellular T-cell aggregates contributes to our understanding of the biology behind immune cell activation.
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